1. Field of the Invention
The present invention relates to an ophthalmic imaging apparatus, and more particularly to an ophthalmic imaging apparatus comprising a first storage means that stores image data from a subject eye imaged by an electronic imaging means, and a second storage means that is slower than the first storage means and records image data transferred from the first storage means.
2. Description of the Prior Art
A CCD image sensor is an example of the type of electronic imaging device that is used by an ophthalmic imaging apparatus such as an eye fundus camera for obtaining images of an eye being examined. In such an apparatus, the images thus obtained are stored on external storage media such as hard or flexible disks, MO media, memory cards, and so forth. For this purpose, the image data is stored as raw bit-map data or in a compressed data format such as JPEG.
Some such apparatuses use a fluorescent imaging mode to perform continuous imaging. In this mode, a fluorescent agent is injected into the patient""s veins to obtain images of the distribution of the fluorescent agent into blood vessels in the eye fundus. To obtain images of the fluorescent agent spreading through the blood vessels of the eye fundus, continuous imaging has to be performed a plurality of times, such as from several times up to several tens of times, within a short period of time ranging from several seconds to several tens of seconds. In most cases, a single image is obtained by pressing the shutter button once, and when the shutter button is kept depressed, continuous imaging is performed providing the images being taken at time intervals determined by hardware operating conditions.
In fluorescent imaging, the fluorescent is injected and this is immediately followed by a start button being pressed to activate a timer that measures the injection timing. The injection timing information is recorded together with the images obtained.
A problem that arises with respect to continuous fluorescent imaging is that of the constraints imposed by the speed of the external storage device to which the image data is written. This imposes limitations on the number of continuous imaging cycles required to accomplish the fluorescent imaging. Another problem is that, when the CCD image data is obtained as color data that is then processed to convert the data to black-and-white images, the data transfer time after imaging tends to increase.
An object of the present invention is to provide an ophthalmic imaging apparatus that enables the number of imaging cycles to be reduced to assure the required number of continuous imaging operations particularly in the case of continuous imaging mode.
According to the present invention an ophthalmic imaging apparatus comprises a first storage means that stores image data from a subject eye imaged by an electronic imaging means, a second storage means that is slower than the first storage means and records image data transferred from the first storage means, means for determining whether or not the eye is imaged by the electronic imaging means in a specific continuous imaging mode, and means responsive to said determination for controlling transfer timing of image data from the first storage means to the second storage means.